A new species of Characidium is described based on specimens obtained from the highland streams of the Serra do Mar, Atlantic Forest Biome, in Paraná State, Southern Brazil. The new species is possibly a member member of the C. lauroi group, which is diagnosed by having the isthmus unscaled, bars poorly marked, and spots on sides of body, and is composed by four additional species: C. japuhybense ; C. lauroi ; C. oiticicai ; and C. schubarti . The new species differs from its congeners with naked isthmus, except C. helmeri , by having 15-18 principal caudal-fin rays; and 10-12 pectoral-fin rays; and from C. helmeri , by having a slender body, tip of pectoral fin not reaching origin of pelvic fin, tip of pelvic fin not reaching beyond anus, supraorbital present and well developed, and by lacking vertically elongated dashes on sides of body. The new species is known from tributaries of the rio Jordão, in the rio Iguaçu Basin, and rio Taquari, a tributary of the rio Ribeira de Iguape coastal drainage.

Herein we describe a new species of Characidium , only known from a few localities in Paraná State: the tributaries of rio Jordão, a tributary of the right bank of rio Iguaçu, rio Paraná-Basin; and the rio Capivari, in the southern part of the rio Ribeira de Iguape, a coastal drainage. The new species is hypothesized as a member of the C. lauroi group of species. The C. lauroi group is composed by four additional species, endemic to the clear water streams of the Serra do Mar between Paraná and Rio de Janeiro States: C. japuhybense Travassos, 1949, from the coastal drainages in São Paulo and Rio de Janeiro; C. lauroi Travassos, 1949, from the tributaries of the upper and middle rio Paraíba do Sul; C. oiticicai Travassos, 1967, from the upper rio Tietê and rio Ribeira de Iguape; and C. schubarti Travassos, 1955, from the headwaters of rio Paranapanema and rio Ribeira de Iguape (Travassos, 1949a, 1949b, 1955a, 1967; Bizerril & Primo, 2001; Buckup & Melo, 2002; Oyakawa et al., 2006).

Materials and Methods

Morphometric and meristic data were obtained from the left side of specimens, under a binocular stereomicroscope, according to Buckup (1993a) and Melo & Oyakawa (2015). Measurements were taken using a digital caliper to 0.1 mm. Counts are listed in the text, followed by their frequencies in parentheses; an asterisk indicates the value for the holotype. Osteological characteristics were observed in cleared and stained specimens (cs), which were prepared according to Taylor & Van Dyke (1985). Terminology for caudal-fin elements follows Fujita (1990), the vertebral counts included the five anterior-most elements modified into the Weberian apparatus counted individually, but the urostyle was counted as a single element, and the supernumerary elements in dorsal and anal fins were counted only from cleared and stained individuals. Institutional abbreviations follow ASIH codes listed at http://asih.org/codons.pdf.

Additionally, C. travassosi differs from all species in Clade C1, except C. helmeri and C. oiticicai , by the absence of the adipose fin (vs. adipose fin present; in C. oiticicai , the adipose fin can be either absent, reduced or well-developed); and from all species in Clade C1, except C. helmeri and C. schubarti , by having the unscaled ventral surface restricted to a small area in the isthmus (vs. unscaled area extending from the isthmus to the area between the contralateral anterior pectoral-fin rays in C. japuhybense , C. lauroi , and C. oiticicai ; unscaled area extending from isthmus, to the breast and around the pectoral fins in C. alipioi , C. amaila , C. boavistae , C. bolivianum , C. fasciatum , C. gomesi , C. grajahuense , C. kamakan , C. purpuratum , C. pterostictum , C. timbuiense , and C. vidali , and unscaled area extending from the isthmus to the belly in C. crandellii , and C. declivirostre ).

Distribution. Characidium travassosi is only known from Paraná State, Brazil, in small cold-water creeks of the Mata Atlântica biome. It is known from the streams draining the west side of Serra da Esperança into rio Jordão, a tributary of the right bank of rio Iguaçu, rio Paraná Basin; and from rio Taquari, a small stream at Serra da Graciosa, which runs north into the rio Capivari, in the southern-most portion of the rio Ribeira de Iguape coastal system (Fig. 2).

Etymology. The specific name is dedicated to Haroldo Travassos, a deceased Brazilian ichthyologist, in recognition to the contributions he made for the taxonomy of the genus Characidium . Travassos worked at the Brazilian Museu Nacional, and was responsible for the description of 13 species of Characidium between 1944 and 1967, mostly from the South and Southeastern Brazil.

Conservation status. Considering that current relevant threats to the species were not detected in its distribution area, Characidium travassosi can be classified as Least Concern (LC), according to the International Union for Conservation of Nature categories and criteria (IUCN, 2014).

Discussion

The number of bony elements of the caudal fin is variable in C. travassosi , being reduced in some specimens (Fig. 3). The complete condition is to have six hypurals and three epurals supporting the principal caudal-fin rays, and the upper and lower procurrent rays, as in Characidium fasciatum (MZUSP 85938, Fig. 3d). Only a few specimens of C. travassosi (e.g. , MZUSP 88142, Fig. 3a) have such condition, and other specimens have variation, including fusions and losses of caudal-fin bones. The number of epurals varies from one to three, being two the most frequent (e.g., MZUSP 88142 and 85938, Fig. 3b, c). The number of hypurals may be reduced to five or four, but with different combinations: in MZUSP 85938, the hypural four or five is missing or fused (Fig. 3c), and in MZUSP 88142 the hypurals one and two, and hypurals three and four are clearly fused (Fig. 3b). The malformation of the caudal-fin bones is correlated with the reduced number of caudal-fin rays.

Reduction in number of caudal-fin rays is a relatively common trend among characidiins, including five species of Characidium . Microcharacidium Buckup, 1993 includes three miniature species with only 17 principal caudal-fin rays (character 36, state 1 of Buckup, 1993b): M. eleotrioides (Géry, 1960), M. weitzmani Buckup, 1993, and M. gnomus Buckup, 2003. Zarske (1997) erected the genus Geryichthys to include G. sterbai and suggested a close relationship between Geryichthys and Microcharacidium based on the low number of caudal-fin rays, pectoral-fin rays, and lateral-line scales. The validity of Geryichthys , however, was previously questioned by Graça et al. (2008) and, although the species is valid, the genus should be considered as a junior synonym of Characidium . Characidium geryi was erroneously described as a Microcharacidium due to the low number of fin rays, also has 16-17 caudal-fin rays (Zarske, 1997). Other species of Characidium with relatively low number of caudal-fin rays are C. helmeri with 18-19 caudal-fin rays, C. mirimNetto-Ferreira, Birindelli & Buckup, 2013 with 15-17 caudal-fin rays, C. nupelia Graça, Pavanelli & Buckup, 2008 with 17-19 caudal-fin rays, and C. xavante da Graça, Pavanelli & Buckup, 2008 with 18-19 caudal-fin rays (Graça et al. , 2008; Netto-Ferreira et al. , 2013; Zanata et al., 2015).

Characidium travassosi also has a low number of pectoral-fin rays (10-12) compared to most of its congeners, which have 13 or more. The smaller range in number of pectoral-fin rays is not a discrete character and, therefore, it is difficult to coded it as a phylogenetic character. It does not seem to unique to any particular group of species of Characidium , since the following species also have a low count of pectoral-fin rays: C. bahienseAlmeida, 1971 has 9-11 pectoral-fin rays; C. bimaculatumFowler, 1941, with 12 pectoral-fin rays; C. etzeli Zarske & Géry, 2001, with 11-12 pectoral-fin rays; C. geryi , with 8-9 pectoral-fin rays; C. heinianum Zarske & Géry, 2001, with 10 pectoral-fin rays; C. helmeri , with 8-12 pectoral-fin rays; C. mirim , with 9-11 pectoral-fin rays; C. nupelia , with 11-13 pectoral-fin rays; C. sterbai , with 9-10 pectoral-fin rays; and C. xavante , with 11-13 pectoral-fin rays (Fowler, 1941; Almeida, 1971; Zarske, 1997; Zarske & Géry, 2001; Graça et al., 2008; Netto-Ferreira et al., 2013; Zanata et al., 2015). The species of Elachocharax , Klausewitzia , Microcharacidium , and Odontocharacidium have nine or fewer pectoral-fin rays (Buckup, 1993b: Clade 5; character 29).

Characidium lauroi group of species. The group was firstly proposed by Travassos (1955a: 371, 1967: 45), without an explicit diagnosis or establishment of its taxonomic limits. In addition to C. travassosi , the C. lauroi group includes the following four species: C. lauroi , C. japuhybense , C. oiticicai , and C. schubarti (Melo, 2001; Buckup & Melo, 2002).

These species occur in small streams draining the Serra do Mar mountain range from 22º17'S to 25º48'S and 45º15'W to 48º30'W, along the eastern areas of the Brazilian states of Paraná, São Paulo and Rio de Janeiro. Characidium lauroi occurs in the tributaries of the Medium and Upper rio Paraíba do Sul drainage; C. japuhybense , in coastal streams from the Ilha Grande Bay to the State of São Paulo, including a few isolated populations in the streams of the Ilha Grande and the Ilha de São Sebastião (Ilha Bela); C. schubarti , in tributaries of rio Paranapanema; and C. oiticicai , in headwaters of rio Tietê. Remarkably, with the exception of C. lauroi , all other species of the group also occur in the rio Ribeira de Iguape coastal drainage (Travassos, 1949a, 1949b, 1955a, 1967; Oyakawa et al., 2006; Scaramuzza et al., 2011; Lima, 1997; Ribeiro et al., 2006; Marceniuk et al., 2011; our data)

Characidium lauroi group is characterized by three derived characteristics: parietal branch of supraorbital sensory canal absent; vertical bars irregular distributed, fainted or absent, not connected ventrally in caudal peduncle; and presence of small spots on the ventral portion of flank. Although those characteristics represent putative synapomorphies, the absence of the parietal branch, and the poorly marked vertical bars are not unique to the C. lauroi group. The presence of dots on sides of body, however, is very characteristic and unique to the group.

The small dots on sides of body develop ontogenetically, on the ventral tip of the transversal bars: as the fish grows, the bars fade and the dots become more evident. In C. travassosi , the dots are inconspicuous; in C. japuhybense the dots are well-marked, circular, and more concentrated in the ventral tip of transversal bars; and in the adults of C. lauroi , C. oiticicai and C. schubarti the dots are well-marked, numerous, and irregularly distributed ventrally and dorsally to the lateral line.

Other species of Characidium having marks on body are C. helmeri , C. longumTaphorn, Montaña and Buckup, 2006, C. pellucidumEigenmann, 1909, C. pteroides Eigenmann, 1909, and C. stigmosum . Characidium longum , C. pellucidum , C. pteroides are members of Clade C5 (Buckup, 1993b), and restricted to the northern part of South America. The disposition and shape of the spots in those species is different to the species of the C. lauroi group: in Characidium longum and C. pellucidum spots are restricted to the area along the lateral midline and dorsum of body, and C. pteroides has distinguishing reddish-brown crescents-shaped marks irregularly distributed on body (Eigenmann, 1912; Taphorn et al. , 2006). Characidium stigmosum have dots elliptical and much larger when compared to the species of the C. lauroi group (Melo & Buckup, 2002). In Characidium helmeri , the marks are formed by melanophores more concentrated on the posterior half of scales, forming vertically elongated, narrow spots or dashes (Zanata et al., 2015).

Within the species of the C. lauroi group, the unscaled area of the isthmus is restricted to a smaller area than in the remaining species of Clade C1 (Buckup, 1993b). In C. travassosi it is restricted to the isthmus and anterior margin of the cleithrum; in C. lauroi , C. japuhybense and C. oiticicai , it extends to the level of the three anterior pectoral-fin rays, but not surrounding the pectoral fins; and C. schubarti has this character variable, with both conditions mentioned above (Travassos, 1949a, 1949b, 1955a, 1967; our data).

Characidium hasemani Steindachner, 1915 and C. laneiTravassos, 1967 have naked isthmus, but according to the phylogenetic hypothesis proposed by Buckup (1993b), they fit elsewhere in the phylogeny. Noteworthy, C. interruptum Pellegrin, 1909 was referred as having unscaled isthmus (Buckup, 1993b; Melo & Buckup, 2002), but all specimens examined by us have the isthmus completely scaled, suggesting that this character needs to be reevaluated.

The two additional synapomorphies of Clade C1 (Buckup, 1993b) are variable among the species of the C. lauroi group. The reduction or absence of postcleithrum 1 (character 23, Buckup, 1993b) is only present in C. lauroi , C. oiticicai and C. schubarti , and the reduction of the fontanel and exclusion of the frontals from its anterior margin (character 8, Buckup, 1993b) is present in C. oiticicai and C. schubarti . These variations reinforce the need for further phylogenetic studies focused on the species of Characidium , with the inclusion of a larger number of species and new characters (Buckup, 1993b; Netto-Ferreira et al., 2013; Zanata & Camelier, 2015).

For loans and specimens we thank Roberto Reis (MCP), Mario de Pinna, Michel Gianeti (MZUSP), Oscar Shibatta (MZUEL), Susan Jewett, Sandra Raredon, Richard Vari (USNM), Wilson Costa (UFRJ), and Vinícius Abilhoa (MHNCI). We would like to thank M. Marinho (MZUSP) for data and information of the types of C. sterbai , C. Zawadzki (UEM) for helping us to obtain selected references. Part of the original research was conducted by MRSM at the Museu Nacional, Universidade Federal do Rio de Janeiro, with a graduate fellowship from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). Additional grants supporting this study were provided to MRSM (Fundação de Amparo à Pesquisa do Estado de São Paulo - FAPESP, 2014/15168-7); PAB (Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq, 307610/2013-6, 476822/2012-2) and (Fundação Carlos Chagas Filhos de Apoio a Pesquisa do Estado do Rio de Janeiro - FAPERJ, E-26/111.404/2012); and OTO (FAPESP, 00/04300-9).

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Eigenmann, C. H. 1912. The freshwater fishes of British Guiana, including a study of the ecological grouping of species, and the relation of the fauna of the plateau to that of the lowlands. Pittsburgh, Carnegie Institute, 597p. (Memoirs of Carnegie Museum, vol. 5).
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Weitzman, S. H. & R. H. Kanazawa. 1978. The South American fish genus Elachocharax Myers with a description of a new species (Teleostei: Characidae). Proceedings of the Biological Society of Washington, 91: 158-183.
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